(1) Field of the Invention
This invention relates to a protective garment, and more particularly to a fabric laminate for protective garments, particularly for fire fighters for protection from the elements and the hazards of fire fighting.
(2) Description of the Prior Art
Protective gear for fire fighters usually comprises a helmet, heavy protective turnout coat, some form of upper leg protection which produces similar protective characteristics as the coat, boots and gloves. The fire fighter is required to wear such heavy protective equipment to insulate himself from the structural fire with which he is engaged. The environmental conditions which fire fighters encounter in suppressing a typically involve abnormal exposures which can produce an extraordinary number of potentially injuring situations. The fire fighter is typically exposed to intense heat, smoke, and moisture, as well as brief flame exposure. Such environmental conditions are very often compounded by the general character of the ambient weather conditions, e.g. extreme cold or extreme heat. The fire fighter's protective outer garment is primarily designed to shed water and other liquids and to thermally insulate the fire fighter from the extraordinary heat associated with his fire suppression activity. Because its protection is so comprehensive, the garment will also protect him from ambient weather conditions, from cold to temperate. But also because of its comprehensive capacity, the garment will overheat the fire fighter in hot weather ambient.
The protective garments presently worn by the fire fighter are comprised of an outer shell of extremely tough fabric for protection, a moisture barrier which serves primarily to shed water and other liquids, and an internal thermal liner. The garment insulation reduces the effect of the environment in which the fire fighter must perform and, because of the physical activity which he must perform, enormous amounts of sweat moisture are generated by the fire fighter's body. Such moisture gathers within the thermal insulating liner. The continued use of a protective garment whose thermal liner has been saturated has a substantial deleterious effect on the fire fighter, both physically and psychologically. Donning a wet garment produces a hypothermic trauma which expends a substantial amount of the fire fighter's energy, and where work, weather ambient or fire heats up the garment, heat stress is often produced. It is commonly held that premature cardiopulmonary aging may result.
The protective garment assembly is the focus of conflicting priorities vis-a-vis as lightweight and comfortable as possible yet providing maximum amount of protection, i.e. to eliminate burn injuries in the most dire circumstances of flashovers for periods exceeding 12 to 15 seconds. Because of the immediate, catastrophic consequence of the latter the protective garment design has evolved to one of providing an envelope of protection that has as its primary function protecting the fire fighter from the extreme environment. Current estimates indicate that the fire fighter is exposed to this extreme environment for only 5% to 20% of the time during which he must wear his gear. The other 80% to 95% of the time, he is subject to heat stress by overheating inside the garment. In any case, the substantially athletic nature of the work, in hostile or weather ambients, is bound to cause severe heat stress, because of the emphasis in the garment's insulative characteristics.
Heat stress is becoming more and more of a recognized factor in protective garment design, and thereby has lead to the recommendation, incorporation, etc. of GORETEX.RTM. (a registered trademark of W. L. Gore Associates, Inc.) breathable membranes to replace the neoprene or butyl moisture barriers previously used in protective garments over the last ten years. The moisture barrier provides a significant layer of thermal protection in a flashover situation, and also prevents the intrusion of hostile liquids to the garment's interior, which could seriously affect the safety of the fire fighter. The GORETEX.RTM. moisture barrier is a barrier to liquid permeation, but not a barrier to vapor permeation. The liquid impervious nature of the GORETEX.RTM. material, and its inherent high temperature performance render it a very effective and dense heat shield in the extreme flashover environment.
While such a fabric, per se, is an effective moisture barrier and capable of reducing heat, still the potential effectiveness is not fully realized since the moisture barrier is disposed between two relatively water-resistant layers of fabric, i.e. the outer shell and the inner thermal liner. Consequently, both the outer shell and the inner thermal layer reduce the moisture vapor permeability of the moisture barrier to the extent that its effective capacity to transfer vapor and thus heat is reduced to less than one-fifth of its capacity if used alone.